The auditory receiver of lizards merits extensive study because of many unusual structural features. Of all vertebrate animals, the lizards probably show a greater number of variations both in the cochlear structure as a whole as in the sound sensitive membrane the papilla basilaris. So far there is some correlation between the degree of complexity and development of papillary structure and its functional capacities. Further studies of the detailed structure of the auditory receiver when correlated with functional and behavioral studies will aid in the overall understanding of auditory mechanisms as well as the possible evolution of these mechanisms. The objectives of the research is to extend our knowledge of the detailed structure of the papilla basilaris. This will concern ultrastructural studies of the membranes (tectorial) related to the sensitive sound receiving units (the hair cells) and many components of the hair cells such as details of their hair-like (ciliary) projections, and descriptions of the polarities of these units which relate to the sound reception mechanism. These studies will involve use of scanning and transmission electron microscopy. Secondary objectives are to study the nature and pattern of hair cell innervation, and to study sound localization on the papilla by studying the location of sound damage lesions.